Railway track circuit



A. T. CARTER RAILWAY TRACK CIRCUIT Filed Jan. ll, 1930 Sept. 22, 1931.

Patented Sept. 22, 1931 UNITED STATESv PATENT OFFICE Y,

AINsLIE T. OARTER, OE lcoLnWaTER, NEW YORK, AssIGNORQTo GENERAL RAILWAY SIGNAL columna', or ROCHESTER, NEW YORK RAILWAY TRACK CIRCUIT Application led January 11, 1930. Serial No. 420,253.

This invention relates to alternating current track circuits for railway signalling, and more particularly to an arrangement or organization for such alternating current track circuits to obtain inherent protect-ion against broken-down insulated joints.

In the well-known normally closed track circuit, commonly used in railway signalling for block signal systems, interlocking, automatic train control, and the like, it is desirable to provide what is commonly known as broken-down joint protection, that is, provide such an organization of devices and circuits that' failure of the insulated joints in the track rails between adjacent circuit sections will not cause improper energization of the track relay of one section by current supplied from the adjacent section, and tend to prevent the proper shunting or deenergization of this track relay by a train. j 'j'One object of the present invention is to 'provide such broken-down joint protection for single phase alternating current track circuits. Generally speaking, and byk way of explanation butnot limitation, the invention contemplates using two-elementtwoposition alternating current track relays of the induction type in combination with rectiiers in series with the windings of these relays and in the transformer connections feeding the track circuits, in such a way that each track relay will close its contactwhen energized by the alternating current supplied to its track circuit, but will open its contacts when energized by the alternating current leaking around the insulating joints from an adjacent track circuit.

Further characteristic features, objects, and advantages of 1 the invention will be in part apparent to ythosey skilled in the art, and in part be pointed out as the description progresses. v

`The accompanying drawing shows ina simplified and diagrammatic manner' one specific embodiment of theA invention applied to two adjacent track circuits, no attempt` having' been made to illustrate any particular arrangement of circuits controlled by the track relays, since these track relays may be employed for an automaticA block signal system, in an interlocking plant, for automatic train control, or for any other purpose in the railway signalling art, and since the particular use to which the track circuits of this invention are put is not material. f j

- Referring to the accompanying drawing, the trackrails 1 and 2, bonded together in the usual way, are divided by insulated jointsB to form blocks or adjacent track circuit sections, of which the blocks B and C and the adjacent end of the block A have been shown. Since the parts and circuits associated with each of these track sections are the same, the same reference characters are used for the corresponding parts, with distinctive exponents.

Referring to the track section B, at one end of this section, preferably the entering end,y the normal direction of tra-flic being from left to right as indicated by the arrow t, a two-element two-position alternating current relayR of the induction type, having windings 5 and 6, lis connected across the track rails 1 and 2,A with one or more rectifiers 7 and 8 in series with each winding, and disposed in an opposite polarity sense. This relay R, shown conventionally, may

be any one of the well-known two-element alternating current relays of the induction type, either comprising a rotor as an operating element, as shown and described, for example, in the application of 1V. K. Howe, Ser. N o. 397,227, filed July 19, 1920, or using a vane as the operating element, such as shown and described for example, in the application of W. K. Howe, Ser. No. 556,990, filed April 27, 1922. This relay R, as will be readily understood by those skilled in the art, is provided withcontact fingers-and stationary contacts, connected to -the operating element of the relay, and biased by a counterweight or spring to an intermediate or neutral position, one suchr contact finger 9 has been shown ,diagrai'nmatically When the two windings '5 and 6 of the track'relaylR are energized with two alternating or uni-.directional pulsating currents,

suitably displaced in time phase, the contact finger 9 is moved from its neutral or deenergized position (shown by a dotted line) in one direction or the other, depending upon the relative phase displacement of the currents in the windings of the relay, to an energized or operated position, as will be readily understood by those skilled in the art. In the specific embodiment of the invention shown, the contact finger 9'of the relay R of the track section B closes its contact when operated to the right, whereas the contact finger 91 of the relay R1 of the adjacent track section C, closes its contact when moved 'to the left. It should be understood that rthe effective energized condition of a track relay is lthat in which its contacts are closed, and that the primary function of the track relay is to open its contacts when a train is present on its track circuit section.V

Y The rectiiers 7 and 8 may be of any suitable type, such as electrolytic, or of the copper-oxide dry plate type; but for the purposes of ,this invention, these rectifiers should provide a small amount of back-leak current, for reasons about to he explained, and if the type of rectifier used does not have this inherent characteristic, a shunt resistance of suitable value should be used.

At the other or exit end of the Vsection B, is a transformer 10, having its primary energized by alternating current from a supply line 11, connected to an alternating enr rent generator 12 orother suitable source. The secondary of this track transformer 1() is connected across the track rails 1 and 2 ill the usual way, with the usual limiting resistance 24 or inductive or condensive or reactance, but inone or both of the leads is interposed a rectifier 13, so that the potential applied across the track rails is unidirectional and pulsating. These rectiliers 13 for adjacent track circuits are disposed in an opposite polarity sense; and these rectitiers 13 may be of the same type as the rectiier 7 and 8, or of a different type, but should provide a back-leak current.

Referring to the track circuit for the track section B, the current from the secondary of thertrack transformer 10. flows over a circuit which may be traced from the left hand side of this secondary, wire 14, rectifier 13, wire 15, track rail 1, wire 16, thence through the winding 5 of the relay l, over wire 17 through rectifier 7, wire 18, winding 5, wire 19 to the wire 20 connected to the track rail 2,7or through the winding 6 of the relay R, over wire 21, through rectifier 8, wire 22, winding 6 to therwire 20, thence along the track rail 2, limiting impedance 24', andwire 23, back to the other terminal of the transformer 10.

Assuming the rectifier 13 to be disposed in the polarity sense shown, itl will be evident that the uni-directional pulsating cure rent iiows in the track rails 1 and 2 in the directions indicated by the arrows a; and it can be seen that this current for the adjacent track sections B and C is of opposite polarity. Referring to the track relay R, this unidirectional current passes freely, so to speak, through the winding 5 of this track relay, but only the back-leak component of this current provided by the rectitier 8, can pass through the other winding 6. Thus, the winding 6 of the relay R is made resistive relative to the winding 5, and an operating torque is developed the same as if the two windings of the relay R were energized by'alternating currents displaced in time phase. It is assumed that this operating torque for the relay R is in a direction to move the contact linger 9 to its righthand closed position. Y

Referring `to the track relay R1 for the track section C, the windings of this relay are energized with uni-directional pulsating current displaced in time phase in the same way, but on account of the reversal of the rectifier 131 for this track circuit, the winding 51 is resist-ive, relative to the winding 61, and other things being the same, the torque developed by the relay R1 is in an opposite direction, moving the contact finger 91 tothe left. y

It will be evident that when a train enters the track section B or C, the corresponding track relay is shunted in the usual way, and opens its contacts, Y s

Assuming now that the insulated joints 3, between the adjacent track sections and C, deteriorate in resistance or break down, so Vthat the current from the transformer 10 and rectifier 13, associated withvthe track section B may be supplied to the track relay R1, associated with the track section C, it will be evident after a little consideration that the polarity of this current is such as to cause the relay R1 to develop torque in a direction to move its contact finger .91 to the right, away from its circuit closing position. Consequently, if the insulated joints break down, or there is sufficient leakage current to interfere with the proper shunting kof the track relay R1, this relay will be automatically operated to the deenergized condition, putting to stop the signal controlled there-` by, or otherwise manifesting by adverse control that the track circuit is out of order. IIn short, broken down joint protectionr is obtained by deenergizing the track relay. The point in the deterioration V of the insulation of the joints, at which the track relay opens its contacts, depends upon a number o fdfactors, but this point is well onthe safe si e. Y

In the specific arrangement shown, the rectiiers 7 and 8 for the track relays in the adjacent track sectiony are disposed in the same polarity sense so that with the reversal of the rectitiers 13 in the track circuit feed, these track relays normally develop torque in opposite directions; but, if desired, as will be evident, these rectilers 7 and 8 for adjacent track relays may be disposed in anopposite polarity sense, so that the normal operating torque is in the saine direction, the saine protection against broken-dowii joints being attained in the same way in both ar-v rangements.

Various other adaptations and inodiications of the particular arrangement and construction ot circuits and devices shown may be developed accordingly from the invention.

that I claiin is 1. In a track circuit system for railroads, a plurality ot track circuit sections, means for supplying uni-directional pulsating currents to each of said sections, said current for adjacent sections being of opposite p0- larity and electro-responsive means for each section closing its contacts when energized by the current supplied to that section and open its contacts when energized by current from an adjacent section.

2. In a track circuit system, a plurality ol track circuit sections, means for supplying said track sections with uni-directional pulsating current, said current for adjacent track sections being of opposite polarity, and a two-element alternating current relay connected to each section and closing its contacts in response to current of the polarity with which the corresponding section is supplied and opening its contacts in response to current of the opposite polarity.

3. In a system of the character described, the combination with bonded track rails divided by insulated joints into a plurality of track sections, a source of alternating current and rectiiying means for supplying unidirectional pulsating current to the track rails of each section, said current for adjacent sections being of opposite polarity, and a two-element alternating current relay connected across the track rails of each section, in series with rectifying means, said relay for each section closing its contacts only when energized with current of the polarity supplied to that track section.

al. In a signalling system for railroads, a plurality of insulated track sections, a source ot alternating current connected across the track rails of each section in series with a rectifier, said rectitiers of adjacent track sections being disposed in an opposite polarity sense and a two-element alternating current relay for each section having its two windings connected across the track rails at the other end of that section in series with rectii'iers disposed in an opposite polarity sense.

5. An alternating current track circuit comprising, a two-element alternating current relay of the induction type having two windings, and means including rectiiers disposed in an opposite polarity sense and connecting said windings across the track rails.

6. An alternating current track circuit comprising, a two-eleinent alternating current relay connected across the track rails closing its contacts in lresponse to a unidirectional pulsating current of a given polarity, and opening its contacts in response to such current of opposite polarity.

7. In a system of alternating current track circuits, the combination with a plurality of track sections, a source of alternating current and rectifying means Jfor supplying current to each track section, said rectitying means for adjacent track sections being disposed in an opposite polarity sense.

8. A track circuit system comprising, a plurality of insulated track sections, sources of alternating current and a track relay for each section and means associated with each track relay for causing it to open its contacts when energized from the source connected to the adjacent track section.

9. A single phase alternating current track circuit system comprising, two-element alternating current relays for each sec- Ytion having both windings connected across Aalternating current and rectifying means supplying uni-directional pulsating current to each track section, adjacent track sections being supplied only with pulsating currents of diiierent polarities.

In testimony Vwhereof I affix my signa-k ture.

lAINSLIE T. CARTER.

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